package com.example.resourceSharingPlatform.config.security.jwt;


import java.security.Key;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Component;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import lombok.Data;
/**
 * 一些操纵token的函数
 *
 */
@Data
@Component
public class JwtTokenUtils {

    @Value("${token.secret}")
    private String secret;

    @Value("${token.expireTime}")
    private Long expiration;

    @Value("${token.header}")
    private String header;


    private static Key KEY = null;

    /*
     * 根据userDetails生成token令牌
     * 
     * @param userDetails 用户
     * @return token令牌
     */
    public String generateToken(UserDetails userDetails) {
    	
        System.out.println("[JwtTokenUtils] generateToken "+userDetails.toString());
        
        Map<String, Object> claims = new HashMap<>(2);
        /*
         * claims里面存储
         * 1.“sub”,username
         * 2.“created”,Date()
         */
        claims.put("sub", userDetails.getUsername());
        claims.put("created", new Date());

      //generateToken(Map<String, Object> claims)通过这个map对象生成token
        return generateToken(claims);
    }


    /**
     * 从令牌中获取用户名
     *
     * @param token 令牌
     * @return 用户名
     */
    public String getUsernameFromToken(String token) {
        String username = null;
        try {
            Claims claims = getClaimsFromToken(token);
            username = claims.get("sub",String.class);
            System.out.println("从令牌中获取用户名:" + username);
        } catch (Exception e) {
            username = null;
        }
        return username;
    }

    /**
     * 判断令牌是否过期
     *
     * @param token 令牌
     * @return 是否过期
     */
    public Boolean isTokenExpired(String token) {
        try {
            Claims claims = getClaimsFromToken(token);
            Date expiration = claims.getExpiration();
            return expiration.before(new Date());
        } catch (Exception e) {
            return false;
        }
    }

    /**
     * 刷新令牌
     *
     * @param token 原令牌
     * @return 新令牌
     */
    public String refreshToken(String token) {
        String refreshedToken;
        try {
            Claims claims = getClaimsFromToken(token);
            claims.put("created", new Date());


            refreshedToken = generateToken(claims);
        } catch (Exception e) {
            refreshedToken = null;
        }
        return refreshedToken;
    }

    /**
     * 验证令牌
     *
     * @param token       令牌
     * @param userDetails 用户
     * @return 是否有效
     */
    public Boolean validateToken(String token, UserDetails userDetails) {

        String username = getUsernameFromToken(token);
        return (username.equals(userDetails.getUsername()) &&
                !isTokenExpired(token));
    }


    /**
     * 从claims生成令牌,如果看不懂就看谁调用它
     *
     * @param claims 数据声明
     * @return 令牌
     */
    private String generateToken(Map<String, Object> claims) {
        Date expirationDate = new Date(System.currentTimeMillis() + expiration);
        return Jwts.builder().setClaims(claims)
                .setExpiration(expirationDate)
                .signWith(getKeyInstance(), SignatureAlgorithm.HS256)
                .compact();
    }

    /**
     * 从令牌中获取数据声明,如果看不懂就看谁调用它
     *
     * @param token 令牌
     * @return 数据声明
     */
    private Claims getClaimsFromToken(String token) {
        Claims claims = null;

        try {
        	  claims = Jwts.parserBuilder().setSigningKey(getKeyInstance()).build().parseClaimsJws(token).getBody();
//            claims = Jwts.parser().setSigningKey(getKeyInstance()).parseClaimsJws(token).getBody();
//            claims = Jwts.parser().setSigningKey(secret).parseClaimsJws(token).getBody();
        } catch (Exception e) {
            claims = null;
        }
        return claims;
    }


    private Key getKeyInstance() {
        if (KEY == null) {
            synchronized (JwtTokenUtils.class) {
                if (KEY == null) {// 双重锁
                    byte[] apiKeySecretBytes = DatatypeConverter.parseBase64Binary(secret);
                    KEY = new SecretKeySpec(apiKeySecretBytes, SignatureAlgorithm.HS256.getJcaName());
                }
            }
        }
        return KEY;
    }

    public String getSecret() {
        return secret;
    }

    public void setSecret(String secret) {
        this.secret = secret;
    }

    public Long getExpiration() {
        return expiration;
    }

    public void setExpiration(Long expiration) {
        this.expiration = expiration;
    }

    public String getHeader() {
        return header;
    }

    public void setHeader(String header) {
        this.header = header;
    }

    public static Key getKEY() {
        return KEY;
    }

    public static void setKEY(Key KEY) {
        JwtTokenUtils.KEY = KEY;
    }
}
